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Smart liquid window to reduce heating and cooling costs of a building

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Singapore, 19 February 2021 – Scientists at the Nanyang Technological University (NTU), Singapore have developed a liquid window panel that can block sunlight to regulate solar transmission while trapping thermal heat to help reduce energy consumption in buildings.

Due to heat transfer through glass, windows have a significant impact on heating and cooling costs of a building. Conventional windows are made with expensive coatings that cut down infrared light passing into or out of a building, thus helping to reduce demand for heating and cooling. However, they do not regulate visible light, which is a major component of sunlight that causes buildings to heat up.

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To overcome these limitations, the NTU researchers turned to water, which absorbs a high amount of heat before it begins to get hot—a phenomenon known as high specific heat capacity. They created a mixture of micro-hydrogel, water and a stabiliser, and found through experiments and simulations that it can effectively reduce energy consumption in a variety of climates. Thanks to the hydrogel, the liquid mixture turns opaque when exposed to heat, thus blocking sunlight. When it cools, it returns to its original clear state.

During daytime when the temperature is higher, the high heat capacity of water allows a large amount of thermal energy to be stored instead of getting transferred through the glass and into the building. The heat could then be gradually dissipated and released at night.

The hydrogel-based liquid is placed within glass panels. This can reduce up to 45 per cent of heating, ventilation and air-conditioning energy consumption in buildings in simulations, compared to traditional glass windows. It is also cheaper than commercially available low-emissivity glass, yet is 30 per cent more energy efficient.

Dr Long Yi, Senior Lecturer at the School of Materials Science and Engineering, said, “Our innovation combines the unique properties of both types of materials—hydrogel and water. By using a hydrogel-based liquid, we simplify the fabrication process to pouring the mixture between two glass panels. This gives the window a unique advantage of high uniformity, which means the window can be created in any shape and size.”

As a proof of concept, the scientists conducted outdoor tests in hot (Singapore, Guangzhou) and cold (Beijing) environments. The Singapore test revealed that the smart liquid window had a lower temperature at 50 degrees Celsius during the hottest time of the day compared to a normal glass window at 84 degrees Celsius. The Beijing tests showed that the room using the smart liquid window consumed 11 per cent less energy to maintain the same temperature compared to one with a normal glass window.

– Construction+ Online

Source: NTU